Liquid and liquefied gas (i.e. supercritical CO2) phase chromatography and extraction is usually founded upon principles of size or charge differentiation among molecules to be separated. Size exclusion chromatography (separation based on size) and ion exchange or hydrophobic chromatography (separation based on charge) can also be combined for complex chemical separation parameters. However, chemical separation is often inadequate resulting in broad or overlapping chemical elution profiles.
Many types of solid phase material are used for liquid chromatography separations and extractions including micron-sized particles of silica gel, alumina, and high and low density polymer beads. Current methodologies can lead to broad chromatographic analyte peaks that can overlap, limiting the purity of the end product and increasing the labor and time required for liquid chromatography purification schemes. Sorption of liquids or gases onto the current material and extraction is difficult.
Despite this difficulty, analyte analysis remains an important part of many procedures including forensic research. For example, during crime scene investigations, surfaces are frequently swabbed in an attempt to salvage material for analyte analysis through various methods including liquid chromatography.
Many of the analytes salvaged during such swabbing includes secretions from skin of individuals who were present in the location being analyzed. These secretions contain perspiration, body oils and trace quantities of loose material that an individual comes in contact with such as organic compounds, amino acids, lipids, drugs, sulfonamides, antipyrine, acetaminophen, aminopyrine, L-dimethylamphetamine, L-methamphetamine, carbohydrates, cholesterol, iron, C19-steroid sulfates, and Δ16-steroids. These trace chemicals, or analytes, are transferred from the skin along with grease, oil, and perspiration to other surfaces when contact is made with other objects. Analysis and identification of these analytes from fingerprint residue is then used to provide insight into the suspect's habits and evidence of illicit activity.
A fingerprint in its narrow sense is an impression left by the friction ridges of a human finger. In a wider use of the term, fingerprints are the traces of an impression from the friction ridge formations, or patterns of the raised portions, found on the fingertips. These friction ridge formations are unique to an individual, so that no two persons have the exact same fingerprint.
Fingerprint identification is the common term for the process of comparing two instances of friction ridge skin impressions for the purposes of determining whether these impressions could have come from the same individual. Current latent print analysis allows investigators to identify persons of interest by comparing the ridge detail patterns of prints with databases of known prints.
Collecting latent prints involves the application of ultra-fine carbon black powder to the latent print deposited body oils and waxes that are transferred to a surface or substrate upon contact. Interaction between the printing powder and the deposited oils results in the visualization of the ridges and whorls within a print. The lifted print image can then be uploaded to biometric analysis databases such as the FBI IAFIS for future reference.
For these reasons, fingerprint impressions, through analyte analysis and visual impression analysis and comparison, offer a means of personal identification.
However, frequently, the detected print does not match any print on file. When this occurs, the print does not assist in investigation until such time as the print can be linked to an individual through outside means (i.e., if the suspect gives a print as part of the current or other investigation). Additionally, inconclusive partial prints are frequent and limit the value of the obtained data through fingerprint identification. The presence and identification of latent prints simply establishes whether a given subset of individuals have ever been at a particular location. Intelligence on age, gender, physiology, habits, or activities can be inconclusive or impossible to obtain from a simple latent print image.
Another problem for current forensic teams is that the two methods of identifying suspects through fingerprint residue and visual impressions are mutually exclusive. Currently the two processes are mutually incompatible because the fingerprint developers destroy material that could potentially be used for DNA analysis and swabbing for analytes disturbs the visual impressions which make fingerprint identification impossible.
A need therefore exists for an improved separation and/or extraction method that can be achieved by using particles with pore size and pore size distribution and surface functionality that can be tailored to match the specific needs of a project. A need exists for an improved “soft” extraction method that will not destroy the substrate of the analytes.